UICollectionView 不重用单元格 [英] UICollectionView do not reuse cells

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本文介绍了UICollectionView 不重用单元格的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我在 iOS 7 上重用单元格和 UICollectionView 时遇到问题.我的代码在 iOS 6 上运行良好，但在 iOS 7 中它在调用 dequeueReusableCellWithReuseIdentifier 后不会重用单元格(不要调用prepareForReuse).

I am having trouble with reuse cells and UICollectionView on iOS 7. My code works fine on iOS 6 but in iOS 7 it does not reuse the cell after calling dequeueReusableCellWithReuseIdentifier (do not call prepareForReuse).

即使是这段代码 https://developer.apple.com/library/ios/samplecode/CollectionView-Simple/Introduction/Intro.html#//apple_ref/doc/uid/DTS40012860 不会在 iOS7 上重用单元格(但在 iOS6 上运行良好)，在每个 dequeueReusableCellWithReuseIdentifier 上，它都会创建一个新单元格并释放旧单元格.是否有一些新的东西可以阻止细胞被重复使用?

Even this code https://developer.apple.com/library/ios/samplecode/CollectionView-Simple/Introduction/Intro.html#//apple_ref/doc/uid/DTS40012860 does not reuse cell on iOS7 (but works well on iOS6), on every dequeueReusableCellWithReuseIdentifier it creates a new cell and deallocates the old one. Is there some new stuff that prevents cells to be reused?

我的单元格足够大，如果不重复使用它们是非常低效的.我注意到 iOS 7 上的延迟，但在 iOS 6 上没有，因为它们没有在 iOS 7 中被重用.

My cells are big enough that they it is very inefficient to not reuse them. I've notice lag on iOS 7, but not on iOS 6, because they are not being reused in iOS 7.

推荐答案

更新 2:
事实证明，这个答案是不正确的.请参阅下面的答案或点击此链接https://stackoverflow.com/a/20147799/814389.

更新

所以我重新审视了这个答案，因为我对这个bug有了更多的了解..

So I have revisited this answer since as I have found out a little more about this bug..

我拿起了所有可用的设备，并对每台设备进行了相同的测试，结果如下:

I grabbed all the devices I had available to me and ran the same tests on each one and these were the results:

DEVICE          OS Version      CELL REUSE
=============   =============   =============
iPad 4          7.0.0           YES
iPad 4          7.0.3           YES
iPad 3          7.0.3           NO
iPad 2          7.0.3           NO
iPad Mini       7.0.0           YES
iPad Mini       7.0.3           YES
iPhone 5s       7.0.3           YES
iPhone 4        7.0.2           YES
iPhone 4        7.0.3           YES

如您所见，由于某种原因，单元重用似乎不适用于较旧的 iPad(无法渲染模糊的 iPad).

As you can see, it looks like for some reason cell reuse is not working on older iPads (ones that aren't capable of rendering the blurs).

我最初认为，由于某种性能问题，Apple 可能只是阻止在旧 iPad 上重复使用，但如果这是有道理的，iPhone 4 也会显示相同的结果.

I initially thought that Apple may have just prevented reuse on older iPads due to some sort of performance issue but if that was to have made sense, the iPhone 4 would also show the same results.

为了在我的应用程序中解决这个问题，我的 collectionViewController 中有一个 NSMutableDictionary，我将我的单元格存储在那里，键是 indexPath .. 在我的情况下，这没问题，因为我只有大约 9 个单元格及其indexPaths 永远不会改变，但如果你需要更灵活的东西，那么检查 PSTCollectionView (https://github.com/steipete/PSTCollectionView)

To get around this issue in my application, I have a NSMutableDictionary in my collectionViewController and I am storing my cells in there with the key being the indexPath.. In my case this is OK as I only have around 9 cells and their indexPaths never change but if you needed something more flexible then maybe it would be a good idea to checkout PSTCollectionView (https://github.com/steipete/PSTCollectionView)

刚刚在物理设备上对此进行了测试.它似乎在 iOS 7 和 6 上都可以正常工作，但在 iOS 7 模拟器上却无法正常工作！！！

Just tested this out on a physical device.. and it seems to work fine on both iOS 7 and 6 but not iOS 7 Simulator!!!

只需在 collectionView 示例中放一些日志:

Just put some logs in the collectionView sample:

@implementation Cell

- (id)initWithCoder:(NSCoder *)aDecoder
{
    NSLog(@"%s",__func__);
    self = [super initWithCoder:aDecoder];
    if (self)
    {
        CustomCellBackground *backgroundView = [[CustomCellBackground alloc] initWithFrame:CGRectZero];
        self.selectedBackgroundView = backgroundView;
    }
    return self;
}

-(void)prepareForReuse
{
    NSLog(@"%s",__func__);
}

-(void)dealloc
{
    NSLog(@"%s",__func__);
}

@end

然后在所有三个设备上滚动到底部，这是输出:

Then scrolled to the bottom on all three devices and this was the output:

iOS 7 模拟器

2013-10-09 17:42:45.798 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.807 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.811 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.841 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.844 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.848 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.852 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:45.857 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.080 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.083 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.181 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.183 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.208 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.208 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.214 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.218 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.245 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.246 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.264 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.268 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.289 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.290 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.317 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.322 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.343 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.344 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.364 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.367 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.401 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.402 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.430 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.432 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.472 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.472 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.498 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.505 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.561 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.562 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.585 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.587 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.624 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.624 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.669 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.674 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.797 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.799 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.809 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.809 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.810 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.810 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.964 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.966 CollViewSmpl[9547:a0b] -[Cell initWithCoder:]
2013-10-09 17:42:47.987 CollViewSmpl[9547:a0b] -[Cell dealloc]
2013-10-09 17:42:47.987 CollViewSmpl[9547:a0b] -[Cell dealloc]

iOS 6 设备(iPhone 5)

2013-10-09 17:45:42.173 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.191 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.205 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.217 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.230 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.242 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.253 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:42.264 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:43.630 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:43.640 CollViewSmpl[187:907] -[Cell initWithCoder:]
2013-10-09 17:45:43.697 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.706 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.777 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.791 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.844 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.855 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.927 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:43.937 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.027 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.037 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.144 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.155 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.311 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.324 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.560 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:44.571 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.027 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.040 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.397 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.407 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.494 CollViewSmpl[187:907] -[Cell prepareForReuse]
2013-10-09 17:45:45.503 CollViewSmpl[187:907] -[Cell prepareForReuse]

iOS 7 设备(iPhone 5s)

2013-10-09 17:44:37.603 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.015 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.029 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.037 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.045 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.053 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.061 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:38.071 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:39.470 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:39.483 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:39.535 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.540 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.583 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.587 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.633 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.637 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.683 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.688 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.733 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.737 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.783 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:39.791 CollViewSmpl[871:60b] -[Cell initWithCoder:]
2013-10-09 17:44:39.866 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.870 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.933 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:39.938 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.033 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.036 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.149 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.152 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.300 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.304 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.650 CollViewSmpl[871:60b] -[Cell prepareForReuse]
2013-10-09 17:44:40.652 CollViewSmpl[871:60b] -[Cell prepareForReuse]

您可以看出在 iOS 6 和 7 中重用之间发生了一些变化，因为 1) 它在模拟器中不起作用 2) 如果您开始时进行非常快速的滚动，则单元格最初并不是准备好重用，所以它必须创建一个新的来弥补 iOS 6 没有的地方(见我的日志).

You can tell that there have been some changes between reuse in iOS 6 and 7 because 1) It doesn't work in the simulator and 2) If you do a really fast scroll to begin with, the cells aren't initially ready for reuse so it has to create a new one to compensate where iOS 6 didn't (see my logs).

我花了半天时间试图修复一个只发生在模拟器上的错误.

There goes half of my day trying to fix a bug that only happens on the simulator.

这篇关于UICollectionView 不重用单元格的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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